The artery-clogging trans fat tally alone is "astonishing" in the dish of fried fish, cornmeal hush puppies and onion rings, according to the Center for Science in the Public Interest. The American Heart Association's recommended limit is less than 2 grams daily and trans fat has been banned by some cities and states and abandoned by many U.S. food makers.

CSPI, a consumer-focused nonprofit group that promotes healthier eating, wants the chain to stop using the unhealthy oil and is urging the U.S. Food and Drug Administration to revoke its approval of trans fat-containing partially hydrogenated cooking oils that raise the risk of heart disease.

CSPI said it planned to pursue legal action if Long John Silver's continues to use the unhealthy cooking oil.

"It's outrageous that Long John Silver's foods are still loaded with artificial trans fat and that the FDA still permits it in foods," Walter Willett, chair of the nutrition department at the Harvard School of Public Health, said in a statement.

Representatives for the FDA and the Louisville, Kentucky-based Long John Silver's did not immediately return requests for comment.

Long John Silver's "Big Catch" meal also has 19 grams of heart disease-promoting saturated fat and the high sodium content promotes high blood pressure and stroke, CSPI said.

Trans fat is considered to be the most unhealthy dietary fat because it increases "bad" LDL cholesterol and reduces "good" HDL cholesterol. Trans fat occurs naturally in meat and milk, but the majority makes its way into the American diet by way of foods cooked with partially hydrogenated vegetable oils.

The U.S. Food and Drug Administration in 2006 began requiring food makers to list trans fat on their product labels. New York City, the state of California and other jurisdictions also passed laws banning the use of trans fats in restaurants and other food service establishments.

As a result, packaged food makers have largely eliminated their use of trans fat and high-profile restaurant chains like McDonald's Corp have switched to trans fat-free oils.

Typical adults are advised to consume no more than 20 grams of saturated fat and 1,500 milligrams of sodium per day.

CSPI also compiles an annual list of "food porn" to alert consumers to menu items with eye-popping levels of calories, saturated fat, sugar and/or sodium. The group has used such "awards" to raise awareness about healthy eating.